Metal-oxide-semiconductor transistor and method of forming gate layout

ABSTRACT

A metal-oxide-semiconductor transistor includes a substrate, a gate insulating layer disposed on the surface of the substrate layer, a metal gate disposed on the gate insulating layer and having at least one plug hole, at least one dielectric plug disposed in the plug hole, and two diffusion regions disposed at two sides of the metal gate in the substrate. The metal gate is configured to operate under an operation voltage greater than 5 v.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a metal-oxide-semiconductortransistor and a method of forming gate layout, and more particularly,to a method of forming gate layout to reduce gate dishing defect and arelated structure of metal-oxide-semiconductor transistor.

2. Description of the Prior Art

With advances in technology, the related industry and technology ofsemiconductor integrated circuit (IC) has been grown rapidly. Highvoltage metal-oxide-semiconductor (HV MOS) transistor devices have beenbroadly utilized in CPU power supply systems, power management systems,AC/DC converters, LCD/plasma TV drivers, automobile electroniccomponents, PC peripheral devices, small DC motor controllers, PCperipheral devices, small DC motor controllers, and other consumerelectronic devices due to being capable of enduring the high voltageprovided by the electrical power system and having switchingcharacterize together.

In another aspect, as the size of device shrinks continuously, metalgate has gradually replaced the conventional polycrystalline siliconmaterial as being the control electrode configured with high dielectricconstant dielectric layer. However, the issues of process integrationoccur when the metal gates are applied to some specific devices, such asmemory devices and high voltage devices.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide ametal-oxide-semiconductor transistor and a method of forming gatelayout, wherein the metal-oxide-semiconductor transistor includesinsulating plugs according to the design of the method of forming gatelayout of the present invention, so as to prevent the occurrence of gatedishing during the manufacturing process of the metal gate.

An embodiment of the present invention provides ametal-oxide-semiconductor transistor. The metal-oxide-semiconductortransistor includes a substrate, a gate insulating layer, a metal gate,at least one insulating plug and two diffusion regions. The gateinsulating layer is disposed on a surface of the substrate. The metalgate is disposed on the gate insulating layer, wherein the metal gatehas at least one plug hole therein and is configured to operate under anoperation voltage greater than 5 volts (v). The insulating plug isdisposed in the plug hole, and the diffusion regions are disposedrespectively at two sides of the metal gate in the substrate.

An embodiment of the present invention further provides ametal-oxide-semiconductor transistor. The metal-oxide-semiconductortransistor includes a substrate, a gate insulating layer, a metal gate,at least one insulating plug and two diffusion regions. The gateinsulating layer is disposed on a surface of the substrate. The metalgate is disposed on the gate insulating layer, wherein at least one of alength and a width of the metal gate is greater than or equal toapproximately 320 nanometers, and the metal gate has at least one plughole therein. The insulating plug is disposed in the plug hole, and thediffusion regions are disposed respectively at two sides of the metalgate in the substrate.

An embodiment of the present invention even further provides a method offorming a gate layout, and the method includes providing a gate layoutdesign diagram, wherein the gate layout design diagram includes at leastone gate pattern. The method further includes disposing at least oneinsulating plug pattern in the gate pattern for producing a modifiedgate layout in a case where any one of a length or a width of the gatepattern is greater than a predetermined size, wherein the predeterminedsize is determined by a process ability limit, and the process abilitylimit is a smallest gate size that would cause gate dishing when achemical mechanical polishing (CMP) process is performed to a gate. Themethod further includes outputting and manufacturing the modified gatelayout onto a photomask.

The metal-oxide-semiconductor transistor of the present inventionincludes the insulating plug(s) disposed in the gate, and therefore theinsulating plug(s) may be used as the stop layer during the CMP processto the gate for preventing the occurrence of the gate dishing andfurther improving the gate structure and the performance of thetransistor.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a top view of a structure ofa metal-oxide-semiconductor transistor according to a first embodimentof the present invention.

FIG. 2 is a schematic diagram illustrating a partial cross-sectionalview of the metal-oxide-semiconductor transistor along a sectional line2-2′ in FIG. 1.

FIG. 3 is a schematic diagram illustrating a top view of a structure ofa metal-oxide-semiconductor transistor according to a first variantembodiment of the first embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a partial cross-sectionalview of the metal-oxide-semiconductor transistor along a sectional line4-4′ in FIG. 3.

FIG. 5 is a schematic diagram illustrating a top view of a structure ofa metal-oxide-semiconductor transistor according to a second variantembodiment of the first embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a partial cross-sectionalview of a metal-oxide-semiconductor transistor of a second embodiment ofthe present invention.

FIG. 7 is a schematic diagram illustrating a partial cross-sectionalview of a metal-oxide-semiconductor transistor of a third embodiment ofthe present invention.

FIG. 8 is a schematic diagram illustrating a partial cross-sectionalview of a metal-oxide-semiconductor transistor of a fourth embodiment ofthe present invention.

FIG. 9 is a schematic diagram illustrating a process flow of a method offorming a gate layout of the present invention.

FIGS. 10-12 are schematic diagrams illustrating the method of formingthe gate layout of the present invention, wherein:

FIG. 10 is a schematic diagram illustrating a gate layout designdiagram;

FIG. 11 is a schematic diagram illustrating a modified gate layout; and

FIG. 12 is a schematic diagram illustrating a photomask including themodified gate layout.

DETAILED DESCRIPTION

To provide a better understanding of the present invention, preferredembodiments will be detailed as follows. The preferred embodiments ofthe present invention are illustrated in the accompanying drawings withnumbered elements to elaborate the contents and effects to be achieved.

Please refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagramillustrating a top view of a structure of a metal-oxide-semiconductortransistor according to a first embodiment of the present invention, andFIG. 2 is a schematic diagram illustrating a partial cross-sectionalview of the metal-oxide-semiconductor transistor along a sectional line2-2′ in FIG. 1. As shown in FIG. 1, according to the first embodiment ofthe present invention, the metal-oxide-semiconductor transistor 100 ofthe present invention is a high voltage metal-oxide-semiconductor (HVMOS) transistor. For example, an operation voltage of the HV MOStransistor is greater than 5 volts (v), such as several tens of volts,and/or a break down voltage of the HV MOS transistor is greater than 10volts, such as several tens of volts or even several hundreds of volts.Furthermore, the metal-oxide-semiconductor transistor 100 in thisembodiment is a transistor including a metal gate structure 134, i.e.the gate structure is formed with metal, alloy or metallic compoundmaterial. The metal-oxide-semiconductor transistor 100 of the presentinvention includes a substrate 102, a gate insulating layer 104, a gate124, at least two spacers 112, two diffusion regions 118 and at leastone insulating plug 110. To be understood easily, some of the elementsof the metal-oxide-semiconductor transistor 100 are omitted, and only aportion of the substrate 102, the gate 124, the drifting regions 122,the diffusion regions 118 serving as a source and a drain respectively,and the insulating plug 110 are illustrated in FIG. 1. Each of devicesof the metal-oxide-semiconductor transistor 100 will be detailed asfollows. The substrate 102 may be a silicon substrate, a siliconcontaining substrate (such as SiC), a III-V group substrate (such asGaN), a III-V group-on-silicon substrate (such as GaN-on-silicon), agraphene-on-silicon substrate, a silicon-on-insulator (SOI) substrate,an epitaxial layer containing substrate or other suitable semiconductorsubstrates for example, but not limited thereto. Shallow trenchisolations (STI) 120 may be selectively disposed in the substrate 102for defining a channel region between the adjacent STIs 120. The gateinsulating layer 104 is disposed above the channel region near thesurface of the substrate 102. In the HV metal-oxide-semiconductortransistor 100 of this embodiment, the thickness range of the gateinsulating layer 104 is from several hundreds of angstroms to less thantwo thousands of angstroms, and its material may be silicon dioxide, butnot limited thereto. The metal-oxide-semiconductor transistor 100includes the metal gate structure 134, so that themetal-oxide-semiconductor transistor 100 may selectively further includea high dielectric constant (HK) layer 105, wherein the high dielectricconstant layer 105 and the gate insulating layer 104 may togetherprovide the gate dielectric function. The metal gate structure 134includes the gate 124 disposed on the gate insulating layer 104. Thegate 124 may include a plurality of layers, such as a metal layer 108and a work function layer 106 disposed between the metal layer 108 andthe gate insulating layer 104. It is noteworthy that the metal gatestructure 134 may further include other layers which are not shown inFIG. 2, such as including a plurality of barrier layers, an etching stoplayers and an interface tuning layer. Various materials or materialcombinations may be selected for the work function layer 106 accordingto different conductivity types of the transistor (such as p-type orn-type). In addition, the spacers 112 of the metal-oxide-semiconductortransistor 100 are at least disposed at two sides of the gate 124,covering the sidewall surfaces of the gate 124. The diffusion regions118 are disposed respectively at two sides of the gate 124 in thesubstrate 102, and the diffusion regions 118 of this embodiment aredisposed at the sides of the STI 120 opposite to the gate 124 forserving as a source and a drain of the metal-oxide-semiconductortransistor 100 respectively. The metal-oxide-semiconductor transistor100 may selectively further include one or two doped drifting regions122 disposed under two sides of the gate 124 in the substrate 102,partially overlapping the gate 124 and surrounding the periphery of theSTIs 120 to provide the drift path of electrons. Generally, thediffusion regions 118 and the drifting regions 122 have the sameconductivity type. For example, the diffusion regions 118 and thedrifting regions 122 of this embodiment are N+ doped regions and N dopedregions respectively. It is noteworthy that the gate 124 has a length L₁and a width W₁, and at least one of the length L₁ or the width W₁ of thegate 124 of the present invention is greater than or equal toapproximately 320 nanometers. In this embodiment, the length L₁ may be2500 nanometers for example, and the width W₁ may be 50000 nanometersfor example, but not limited thereto. In addition, the diffusion regions118, the drifting regions 122 and the STIs 120 are disposed in a P-typewell 136 of the substrate 102, i.e. the channel region under the gateinsulating layer 104 and the diffusion regions 118 have oppositeconductivity types.

In addition, at least one insulating plug 110 is further disposed in themetal gate structure 134, inside at least one plug hole 134 a within thegate 124. As shown in FIG. 1, the gate 124 of this embodiment has aplurality of plug holes 134 a, the metal gate structure 134 includes aplurality of insulating plugs 110 respectively disposed in one plug hole134 a, and the insulating plugs 110 of this embodiment are arranged in aherringbone pattern in the gate 124. The insulating plugs 110 are formedwith insulating material layer(s) filled in the plug holes 134 a, suchas the material of the spacer 112 covering the surfaces of the plugholes 134 a. Moreover, the metal-oxide-semiconductor transistor 100 mayselectively include a contact etching stop layer (CESL) 114 and aninter-layer dielectric (ILD) layer 116 disposed on the surface of thesubstrate 102. The sidewall surface of the gate 124 is covered by theCESL 114, and the CESL 114 of this embodiment further fills the plugholes 134 a to form a portion of the insulating plugs 110. In otherwords, the insulating plugs 110 of the present invention are formed witha portion of the spacer 112 and a portion of the CESL 114. However, in avariant embodiment, the ILD layer 116 may also be formed in the plugholes 134 a to form the plug holes 134 a when the size of the plug holes134 a is large enough, and therefore the insulating plugs 110 are formedwith a portion of the spacer 112, a portion of the CESL 114 and aportion of the ILD layer 116. In addition, the ILD layer 116 is disposedat the periphery of the metal gate structure 134 to insulate the metalgate structure 134 from other electronic devices. Furthermore, themetal-oxide-semiconductor transistor 100 may also selectively includeother contact devices (not shown) disposed on the metal gate structure134 or adjacent to the metal gate structure 134, electrically connectedto the gate 124 or the diffusion regions 118. The above mentionedcontact devices are preferably disposed away from the insulating plugs110.

It is noteworthy that the purpose of the design of disposing theinsulating plugs 110 in the gate 124 of this embodiment is to preventthe occurrence of gate dishing when performing the gate CMP process tothe gate 124. For example, when the maximum value of the process abilitylimit (also understood as technology layout rule, TLR) of the currentCMP process is 2 micrometers which will not lead to dishing, it meansthe surface dishing will occur as the CMP process is performed to themetal gate 124 under the condition that any one of the length L or thewidth W of the metal gate 124 is greater than 2 micrometers. Therefore,a distance between any two adjacent insulating plugs 110 is preferablydesigned to be less than or equal to the process ability limit, 2micrometers, according to the concept of the present invention. Inanother aspect, the size of the insulating plugs 110 (i.e. the diameterof the plug hole 134 a) may be small since it is designed to avoidfringe voltage caused due to the relatively large size of insulatingplugs 110. For example, the size or the diameter of the insulating plugs110 may be approximately 80 nanometers to 120 nanometers, but notlimited thereto.

The method of manufacturing the metal gate structure 134 of thisembodiment utilizes the gate-last process and HK-first process. In otherwords, a high dielectric constant layer and a polysilicon layer areformed on the surface of the substrate 102 first, then a photomaskincluding a gate pattern and plug hole patterns is utilized to perform aphotolithography and etching process to pattern the polysilicon layerand the high dielectric constant layer for forming a polysilicon dummygate and the plug holes 134 a simultaneously. However, in a variantembodiment, the gate pattern and the plug hole patterns may be definedby different photolithography process individually. Next, the processesfor manufacturing other devices of the transistor are proceeded, such asforming the spacers 112 and the CESL 114 on the sidewall of the dummygate and in the plug holes 134 a, forming the ILD layer 116 andperforming a CMP process. Next, the polysilicon dummy gate is removed toform a gate trench, one or more metal materials are deposited to fillthe gate trench, and then the one or more metal materials above the ILDlayer 154 are removed by performing a CMP process. As a result, as shownin FIG. 2, a top surface of the insulating plug 110, a top surface ofthe gate 124 and a top surface of the ILD layer 154 of the presentinvention are substantially coplanar. However, the design of disposingthe insulating plugs 110 in the gate of the present invention is notlimited to the above mentioned processes, and it may also be applied tothe HK-last process for example, and i.e. the high dielectric constantlayer is formed after the dummy gate is removed. Besides, the design ofdisposing the insulating plugs 110 in the gate of the present inventionmay also be applied to processes for manufacturing a non-planartransistor, such as a dual-gate FinFET or a tri-gate FinFET.

According to the above description, the present invention also providesa method of forming a gate layout. Please refer to FIG. 9 to FIG. 12,wherein FIG. 9 is a schematic diagram illustrating a process flow of themethod of forming the gate layout of the present invention, and FIGS.10-12 are schematic diagrams illustrating the design of the patterns ofthe gate layout of the present invention. The method of forming the gatelayout of the present invention includes the following steps:

Step S1: Provide a gate layout design diagram 200 first, wherein thegate layout design diagram 200 includes at least one gate pattern 224,as shown in FIG. 10.

Step S2: Dispose at least one insulating plug pattern 210 in the gatepattern 224 for producing a modified gate layout 200′ in a case whereany one of the length L′ and the width W′ of the gate pattern 224 isgreater than or equal to a predetermined size, wherein the predeterminedsize is determined by a process ability limit, and the process abilitylimit is a smallest gate size causing gate dishing when a chemicalmechanical polishing (CMP) is performed to the gate, as shown in FIG.11. The predetermined size of this embodiment is 320 nanometers forexample, but not limited thereto. Furthermore, a plurality of insulatingplug patterns 210 are disposed in the gate pattern 224 in thisembodiment, and a distance between any two adjacent insulating plugpatterns 210 is less than or equal to the predetermined size.

Step S3: Output and manufacture the pattern of the modified gate layout200′ onto a photomask 300, as shown in FIG. 12. The photomask 300includes a gate pattern 324 and insulating plug patterns 310corresponding to the gate pattern 224 and the insulating plug patterns210 in the modified gate layout 200′ respectively.

Next, the photomask 300 may be applied to a photolithography process fortransferring the modified gate layout 200′ onto a material layer, suchas the aforementioned polysilicon material layer. It is noteworthy thatthe size of the insulating plug patterns 210 is determined by the sizeof a minimum exposure limit of the photolithography process whiledesigning the insulating plug patterns 210. Therefore, the size of theinsulating plug patterns 210 may be designed to be greater than or equalto a smallest size, wherein a pattern with such smallest size can beformed by the photolithography process while a pattern with a sizesmaller than such smallest size would not be formed by thephotolithography process. However, the insulating plug patterns 210 mayalso be designed to have a relatively large size according torequirements provided that the size and the density of the insulatingplug patterns 210 do not affect the electrical performance of the gate.In addition, according to the aforementioned method of disposinginsulating plug(s) 110 of the present invention, the distance betweenadjacent the insulating plugs 110 and the number of the insulating plugs110 disposed in the direction of the length L₁ do not manifestly affectthe electrical characteristics of the metal-oxide-semiconductortransistor 100. For example, the practical operation voltage, saturationcurrent, leakage current and break down voltage of themetal-oxide-semiconductor transistor 100 are not affected or alteredmanifestly as the number or the density of the insulating plug 110changes.

The metal-oxide-semiconductor transistor of the present invention is notlimited to the aforementioned embodiment. The following descriptioncontinues to detail other embodiments or variant embodiments. Tosimplify the description and show the difference between the otherembodiments, variant embodiments and the above-mentioned embodiment,identical components in each of the following embodiments are markedwith identical symbols, and the identical features will not beredundantly described.

Please refer to FIG. 3 and FIG. 4. FIG. 3 is a schematic diagramillustrating a top view of a structure of a metal-oxide-semiconductortransistor according to a first variant embodiment of the firstembodiment of the present invention, and FIG. 4 is a schematic diagramillustrating a partial cross-sectional view of themetal-oxide-semiconductor transistor along a sectional line 4-4′ in FIG.3. A portion of devices shown in the cross-sectional structure areomitted in FIG. 3, such as the spacer, the STI and the CESL layer. Thework function layer 106 of the metal gate structure 134 is omitted inthe FIG. 4. The above-described simplification representations infigures are also applied to the following embodiments and the variantembodiments, and will not be redundantly described. The differencebetween this embodiment and the previous embodiment is that theinsulating plugs 110 are arranged in a checker pattern in the gate 124.Distances between each insulating plug 110 and other adjoininginsulating plugs 110 which are located on the up side, under side, leftside and right side thereof are the same, such as 2 micrometers, but notlimited thereto. In the cross-sectional structure in FIG. 4, fiveinsulating plugs 110 are sequentially disposed from left to right in thegate 124, and a portion of the spacer 112, a portion of the CESL 114 anda portion of the ILD layer 116 are included in each insulating plug 110.

Please refer to FIG. 5, which is a schematic diagram illustrating a topview of a structure of a metal-oxide-semiconductor transistor accordingto a second variant embodiment of the first embodiment of the presentinvention. The main difference between the present embodiment and thefirst embodiment is related to the arrangement of the insulating plugs110. The insulating plugs 110 of this embodiment are arranged inmultiple rhombuses. In another words, the insulating plugs 110 arearranged in a plurality of straight lines M that are not parallel to thelong edge or the short edge of the pattern of the gate 124, wherein thedotted lines in FIG. 5 refer to the straight lines M.

Please refer to FIG. 6, which is a schematic diagram illustrating apartial cross-sectional view of a metal-oxide-semiconductor transistorof a second embodiment of the present invention. Themetal-oxide-semiconductor transistor 1001 of this embodiment is a normalvoltage metal oxide semiconductor field effect transistor (NV MOSFET),and the length L₂ of the metal-oxide-semiconductor transistor 1001 isless than the length L₁ of the gate 124 in the first embodiment.However, at least one of the length L₂ and the width (not shown in FIG.6) of the gate 124 of this embodiment is still greater than 320nanometers, or an operation voltage of the gate 124 is greater than 5volts. The metal-oxide-semiconductor transistor 1001 includes the gateinsulating layer 104′ disposed on the surface of the substrate 102, thegate 124 disposed between the STIs 120, the diffusion regions 118disposed at two sides of the gate 124 near the surface of the substrate102 for serving as the source and drain, the spacers 112 disposed on thesidewall surfaces of the gate 124 and the sidewall surfaces of the plugholes 134 a, and the CESL 114 covering the spacers 112. Themetal-oxide-semiconductor transistor 1001 may further include an ILDlayer 116 surrounding the gate 124 and two lightly doped regions 126disposed in the substrate 102 and at two sides of the gate 124, whereinthe lightly doped regions 126 surround the diffusion regions 118 in thesubstrate 102 respectively.

Please refer to FIG. 7, which is a schematic diagram illustrating apartial cross-sectional view of a metal-oxide-semiconductor transistorof a third embodiment of the present invention. Themetal-oxide-semiconductor transistor 1002 of this embodiment is alaterally diffused metal oxide semiconductor (LDMOS) transistor, such asan N-type LDMOS transistor. In this embodiment, at least one of thelength or the width (not shown in FIG. 7) of the gate 124 of themetal-oxide-semiconductor transistor 1002 is greater than 320nanometers, or the operation voltage of the gate 124 is greater than 5volts. A plurality of insulating plugs 110 are disposed in the gate 124,and the insulating plugs 110 are formed with the spacers 112 and theCESL 114, but not limited thereto. In addition, themetal-oxide-semiconductor transistor 1002 may selectively include a STI120 disposed at one side of the gate 124 in the substrate 102. In FIG.7, the STI 120 is disposed at the right side of the gate 124 andpartially overlaps the gate 124. However, in other variant embodiments,the STI 120 may not overlap the gate 124 or themetal-oxide-semiconductor transistor 1002 may not include the STI 120being adjacent to the gate 124. The metal-oxide-semiconductor transistor1002 further includes: two N+ type diffusion regions 1181, 1182respectively disposed at two sides of the gate 124, wherein the N+ typediffusion region 1181 serving as the source is disposed at the side ofthe STI 120 opposite to the gate 124; an N-type drifting region 122surrounding the STI 120 and the N+ type diffusion region 1181; aselective P-type diffusion region 127 disposed in the substrate 102 andsurrounding the N+ type diffusion region 1182 serving as the drain; anda p-type well 128 surrounding the P-type diffusion region 127.

Please refer to FIG. 8, which is a schematic diagram illustrating apartial cross-sectional view of a metal-oxide-semiconductor transistorof a fourth embodiment of the present invention. Themetal-oxide-semiconductor transistor 1003 of this embodiment is a finfield effect transistor (finFET). The substrate 102 includes a finstructure 130, the gate 124 is disposed on the fin structure 130, andthe fin structure 130 may selectively include an epitaxial layer 132.The diffusion regions 118 serving as the source and drain arerespectively disposed at two sides of the gate 124 on the surface of theepitaxial layer 132. At least one of the length or the width (not shownin FIG. 8) of the gate 124 of the metal-oxide-semiconductor transistor1003 of this embodiment is greater than 320 nanometers, or the operationvoltage of the gate 124 is greater than 5 volts. The gate 124 stillincludes a plurality of insulating plugs 110 disposed therein. However,only one insulating plug 110 is shown in FIG. 8 for illustration.

In the conventional method of manufacturing the metal gate, thepolysilicon dummy gate is formed first, and the dummy gate is removed toform the gate trench after other devices of the transistor aremanufactured. Then, the metal material is deposited and filled in thegate trench, and the CMP process is performed to remove the excessivemetal material to finish the manufacturing of the metal gate. However,the channel length of the gate structure of the HV MOS transistor isrelatively long to provide a high operation voltage, i.e. the size ofthe gate structure is relatively large. Under the above circumstances,the gate surface dishing will occur during the CMP process, and theelectrical performance of the transistor will also be affected. Incontrast, the main concept of the present invention, from theaforementioned embodiments, is to dispose one or pluralities ofinsulating plug(s) in the gate of the transistor whose size is large orhaving a high operation voltage. For example, when the size of the gateis greater than the process ability limit, the insulating plug can bedisposed in the gate to serve as the stop layer in the following CMPprocess, which can prevent the gate from dishing due to theover-polishing. The number, size, density and arrangement of theinsulating plugs in the gate of the present invention are not limitedprovided that the electrical performance of the transistor is notaffected. In addition, the metal-oxide-semiconductor transistor of thepresent invention may be metal-oxide-semiconductor transistors havingvarious types of structures, such as HVMOS transistor, LDMOS transistor,NVMOS transistor or finFET, but not limited thereto. According to thepresent invention, the disposing of the insulating plug truly improvesthe issue of gate surface dishing in the prior art, and further improvesthe yield in manufacturing the transistor.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A metal-oxide semiconductor transistor,comprising: a substrate; a gate insulating layer disposed on a surfaceof the substrate; a metal gate disposed on the gate insulating layer,the metal gate having at least one plug hole and being configured tooperate under an operation voltage greater than 5 volts (v); at leastone insulating plug disposed in the plug hole; two diffusion regionsdisposed respectively at two sides of the metal gate in the substrate;and at least one shallow trench isolation disposed between the metalgate and the substrate, wherein a portion of the metal gate is disposedon the shallow trench isolation, and a portion of the gate insulatinglayer is disposed below a top surface of the shallow trench isolation.2. The metal-oxide semiconductor transistor according to claim 1,wherein a top surface of the insulating plug and a top surface of themetal gate are coplanar.
 3. The metal-oxide semiconductor transistoraccording to claim 1, further comprising at least one spacer coveringsidewall surface of the metal gate, the insulating plug comprising aportion of the spacer and/or a portion of an inter-layer dielectric(ILD) layer.
 4. The metal-oxide semiconductor transistor according toclaim 1, wherein a diameter of the plug hole is approximately 80nanometers to approximately 120 nanometers.
 5. The metal-oxidesemiconductor transistor according to claim 1, wherein the metal gatecomprises a plurality of plug holes, and the metal-oxide semiconductortransistor comprises a plurality of insulating plugs respectivelydisposed in the plug holes.
 6. The metal-oxide semiconductor transistoraccording to claim 5, wherein the insulating plugs are arranged in aherringbone pattern or a checker pattern in the metal gate.
 7. Themetal-oxide semiconductor transistor according to claim 1, wherein themetal gate comprises at least one work function material.